One of Britain’s major intercity train operators, Avanti West Coast, has parted company with its boss a month after the company admitted it was unable to run its timetabled services. Avanti announced that its managing director, Phil Whittingham, had decided to step down, with effect from 15 September, the date when the next in a series of strikes will further afflict its operations. It is understood that the owners are looking at a range of options and that other senior operational staff are also understood to be in the line of fire. Avanti, a joint venture between FirstGroup and Trenitalia, slashed its schedules last month, leaving only one train an hour instead of three running between London and Manchester. The move was billed by Avanti as a way of running a more predictable service after widespread delays and cancellations but provoked fury, with Labour and the mayor of Greater Manchester, Andy Burnham, calling for it to be stripped of its contract. Whittingham inflamed industrial relations at the firm by blaming the problems on “unofficial strike action” by drivers – a claim denounced as an outright lie by the Aslef union. Aslef welcomed news of the changes. The general secretary, Mick Whelan, said: “The managing director of Avanti West Coast has gone because he lied about unofficial industrial action. We look forward to working with the new MD. There is now an opportunity for passengers and staff to move into a better future.” Whittingham, who transferred to Avanti as managing director from Virgin when the firm took over the west coast mainline operation from Richard Branson’s company, earned £273,000 in the role, and has spent more than 23 years in various roles on the railway. Steve Montgomery, FirstGroup’s overall rail managing director, who is also leading the industry in negotiations over pay in the rail dispute, will step in to “provide executive leadership support” for Avanti. Montgomery said Whittingham had left Avanti “with the team ready for the challenges in delivering the future service requirements”. Whittingham did not respond to requests for comment. The action comes after increasing public anger at the service, with Avanti garnering more complaints than any other train operator in the past two years, even before the recent decline. Avanti employs several hundred drivers but relies on their goodwill to work overtime to run the full schedules. The transport secretary, Grant Shapps, had endorsed Whittingham’s view that “unofficial strike action” – the refusal of drivers to volunteer for additional shifts – was to blame for the poor service. Labour’s shadow transport secretary, Louise Haigh, said Avanti had caused travel misery for millions and Shapps had failed to hold them to account. She added: “If the government had any interest in doing their job, they would finally stand up for passengers, claw-back taxpayers’ money for services that haven’t run, strip the operator of the contract and put in place an urgent plan to restore the timetable.” The firm paid out £11m in dividends last year to its shareholders, who are 70% FirstGroup and 30% the Italian state-owned operator Trenitalia. Unions with members working for Avanti have all voted overwhelmingly for strikes and the service will be halted again in two weeks’ time when drivers walk out for 24 hours on 15 September, as part of wider industrial action. RMT train staff will also walk out as part of the national dispute. A third union, the TSSA, on Friday called more strikes specifically at Avanti, underlining the problems the operator faces. The union’s station staff members will walk out alongside the RMT on 15 and 17 September.